1. Field of the Invention
This invention relates to a relay device used in order to create an on-vehicle LAN such as an active star coupler and a connector providing the relay device.
2. Background of the Invention
The FlexRay standard which can ensure a superiority of both rapidity and liability as a next-generation on-vehicle LAN is enacted. The FlexRay is a communication protocol which is applied to in-vehicle communication requiring high liability, such as steering-by-wire, brake-by-wire, etc., in the field of automobile industry. As the FlexRay adopts a time-trigger type communication system, high liability can be maintained by designing a bus-system in which a time-slot of predetermined time is defined in a communication bus (e.g., see Japanese Unexamined Patent Application Publication No. 2009-94748, Japanese Unexamined Patent Application Publication No. 2008-277873, and Japanese Publication of PCT Application No. 2008-537430).
The FlexRay is a star type network as shown in FIG. 10, or a bus type network as shown in FIG. 11. An active-star coupler (ASC) as the relay device as shown in FIG. 10 performs relaying and branching with a bus-driver, and a passive-star coupler (PSC) as the relay device as shown in FIG. 11 performs relaying and branching without the bus-driver.
In recent years, there is a tendency for the number of devices connected to on-vehicle LAN (i.e., the number of nodes) to increase. Among the aforementioned two types of networks, the star type is connected in point-to-point manner, thereby realizing strength against delay and deterioration of waveform. On the other hand, due to the connection and accordingly increasing number of the nodes wire harness routing is difficult to decrease.
If the FlexRay is used as a replacement of a conventional CAN (Controller Area Network), it is necessary to connect a lot of nodes with the bus type network. In this case, inserting an ASC between PSCs as shown in FIG. 12 can increase the number of nodes.
Although in FIG. 12 the number of relay (i.e., relay times) during the transmission between nodes increases, as a conventional ASC only has a function of the bus-driver and of waveform shaping in a voltage axis direction (i.e., amplitude direction), influences of bit width distortion and ringing pulses to a signal transmitted between nodes increases. As a result, there happen bit error which is caused by the bit width distortion and accordingly change in the period of one bit, and an abnormal waveform in a time axis direction in which due to the influence of ringing pulse the terminus of communication frame is misaligned and the communication frame is extended. Therefore, even if FIG. 12 configuration is applied, there is a problem that such a many nodes cannot be connected.